The PI is conducting research on simian immunodeficiency virus (SIV) in the sponsors laboratory, and sets forth a specific series of experiments and career development activities designed to result in her becoming a successful, independent researcher in the HIV/AIDS field. The experimental aspects of this project focuses on SIVsmmPBj14, which causes severe acute disease in vivo, and efficiently triggers the proliferation of resting simian lymphocytes in vitro. These properties depend on the presence of an immunoreceptor tyrosine-based activation motif (ITAM) in SIVsmmPBj14 Nef. The following hypotheses will be tested: (i) that the lymphoproliferation-inducing phenotype of SIVsmmPBj14 is dependent not only on the Nef ITAM, but also on additional determinants in Nef, and (ii) that the Nef ITAM has effects not only on T cells, but also on monocytes, which enhance viral replication in these cells. Specific aim 1 will examine whether well- defined regions of Nef, including a conserved SH3-binding motif (PxxP), are required for SIVsmmPBj14 to replicate efficiently in simian monocytes, and for the induction of lymphoproliferation. Aim 2 will assess whether trans-complementation of genetically nef-negative SIVsmmPBj14 can restore the functional activity of Nef (as measured by induction of lymphoproliferation and efficiency of viral replication in primary monocytes). Finally, aim 3 will examine whether expression of SIVsmmPBj14 Nef alters intracellular signaling pathways in primary monocytes, and whether this is dependent on the ITAM. Emphasis will be placed on activation of cellular protein kinases, and transcription factors which may enhance viral gene expression. Overall, the experiments proposed are expected to shed light on the pathogenic mechanisms which contribute to the development of AIDS.